#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <stdlib.h>
typedef struct SL
{
	int data;
	struct SL* next;
}SL;

void PushBack(SL** pplist,int a);
void DelBack(SL** pplist);
SL* Buy(int a);
void DelHead(SL** pplist);
void AddHead(SL** pplist, int a);